The present invention generally relates to contact lens manufacturing. More particularly, the invention relates to a machine and method for manufacturing molded toric contact lenses.
A method of cast molding toric contact lenses is described in U.S. Pat. No. 5,611,970 issued Mar. 18, 1997 to Bausch & Lomb Incorporated, assignee herein, the entire disclosure of which is incorporated herein by reference. The method of the '970 patent involves providing anterior and posterior mold sections having concave and convex molding surfaces, respectively, which are placed together to form a lens-shaped mold cavity into which a monomer is deposited and cured to form a lens. The invention of the '970 patent places a ballast-forming feature on the anterior mold section and a toric-forming feature on the posterior mold section, with the anterior and posterior mold sections being alignable at multiple rotational positions. The mold sections themselves are injection molded using special optical tools which replicate the anterior and posterior mold surfaces on the respective mold sections which, in turn, form the optical anterior and posterior surfaces of the resultant lens. Although each mold section is used only once to make a single lens, by placing the ballast and toric features on the opposite mold sections, which may be aligned at any selected one of multiple rotational positions, a plurality of toric contact lenses may be formed, each having different rotational offsets between the ballast and toric features of the lens, by mold sections which are formed from the same optical mold tools. Although the '970 patent at Col. 5, lns. 6-16 suggests ensuring the selected rotational alignment between the mold sections by engaging a notch of the anterior mold section and rotating it on a support relative to indicia on the posterior mold section, there is no discussion of automated manufacturing or handling processes by which this may be carried out.